This invention relates to a coordination complex which is a salt of a cation which consists of at least two metals, one of which is copper I, complexed with a polydentate binucleating ligand. This complex, which reversibly coordinates carbon monoxide, is useful in homogeneous catalysis reactions.
Polydentate amines are known to form stable chelate complexes with a wide variety of metal salts of both main periodic group metals (for example, lithium and sodium as described in U.S. Pat. Nos. 3,734,963 and 3,758,585, respectively) and transition metals including copper (I) as disclosed by C. Floriani et al., J.A.C.S., 103, 185 (1981). In view of their selective complexation of Li and Na salts these amines have a known use in separating alkali metal salts. See, e.g., U.S. Pat. Nos. 3,767,763 and 3,755,533.
Acyclic polydentate amines capable of simultaneously coordinating two metal sites include the bi-sodium complex described by R. Robson, et al., J. Inorg. Chem., 13, 1301, (1974), wherein the ligand contains a sterically unfavorable phenolic oxygen in the binuclear site, and the bi-copper (I) complex described by J. A. Osborn et al., J. Chem Soc. Chem. Comm., 498 (1977), wherein the ligand lacks an optimal configuration of ligating functionalities.
Karlin, et al., J. Chem. Soc. Chem. Comm., 881 (1981) describes oxidation of a binuclear Cu (I) species containing a meta-xylyl-binucleating ligand having two tri-dentate ligand donor groups separated by a metaxylene bridge to produce a binuclear Cu (II) complex. In the Cu(I) and Cu(II) complexes the donor groups are unsaturated (pyridyl) groups. The binuclear Cu(I) complex is not characterized in the article, but oxidation thereof to form the Cu(II) complex results in oxidation of the xylene ring. Karlin et al., J. Coord. Chem., 11, 61 (1981) further describes the structure of a Cu(II) complex containing a para-xylyl binucleating ligand. Karlin et al., J.A.C.S., 104, 5240 (1982) describes a three-coordinate binuclear Cu(I) complex containing a meta-xylyl binucleating ligand with pyridyl donor groups and its reaction with air to form the Cu(II) complex. Sorrell et al., Inorg. Chem., 21, 3250 (1982) discloses a three-coordinate binuclear Cu(I) complex containing a meta-xylyl binucleating ligand with pyrazonyl donor groups and its reaction with oxygen to form the Cu(II) complex. Sorrell et al., J.A.C.S., 105, 2054 (1982) discloses another three-coordinate binuclear Cu(I) complex with a meta-xylyl binucleating ligand having pyrazolyl donor groups. J. Timmons and coworkers have described a 2,6-bis(5-(1,4-diazahexyl)pyridine ligand complexed with Cu.sup.+2 (see Inorg. Chem., 17, 889 (1978) and Inorg. Chem., 21, 1525 (1982)).
Various workers have disclosed binuclear Cu(I) and Cu(I)-Cu(II) complexes of macrocyclic ligands containing 2,6-pyridine, 2,5-furan, and 2,6-phenol fragments. See Drew et al., J.C.S. Chem. Comm., 829 (1980), J.C.S. Dalton, 1868 (1981), J.C.S. Chem. Comm., 388 (1981), Gagne et al., J.A.C.S., 99, 8367 (1977) and J.A.C.S., 101, 4571 (1979).